http://goo.gl/KCmpm - table with common fertilizers. Count all up to 100. If you need more, you can copy this document to your google account and count more.
All fertilizers have base value - how many % you get first time without three-field system. Formula for all fertilisers without infuence or without three-fiels system:
Base value/(sqrt(number of fertiliser)=how many % you get with next fertilitser.
For influence and three-field system formula is:
Base value/(sqrt(number of fertiliser)+Base value*0.2
In fact you can put million hay on your field and you always get +10% influence from each.